Electronic vacuum tube



1935- A. A. THOMAS ELECTRONIC VACUUM TUBE Filed Dec. 31, 1929 INVENTOR UNITED STATES mass- PATENT OFFICE ELECTRONIC VACUUM TUBE Adolph A. Thomas, New York, N. Y., assignor to Radio Corporation of America, New York, N. Y.,' a corporation of Delaware Application December 31, 1929, Serial No. 417,817

, 31 Claims. (Cl. 250-275) This invention is for an electronic vacuum tube of novel construction and capable of a variety of uses, among which I may particularly-mention amplifying electric impulses, producing alternating current from a source of direct current, and rectifying alternating currents. The characteristic feature of my invention is a vacuum tube having two grids and two plates arranged to provide two electron paths. The two grids are connected to opposite sides of an input coil and are therefore always at opposite potential. When-my tube is used as an amplifier or producer of alternating current from direct current, the anodes are connected to opposite sides of an output coil, and the center of this coil is connected to the positive terminal of a source of substantially constant current. The negative side of the source of plate current is connected to one end of the filament. As a result of this novel tube structure, the current through the output coil in the plate circuit is reversed with I reversal of potential on the two'grids, whereby increased amplification is obtained in the secondary coil of the output transformer. This permits the use of fewer tubes to obtain the required degreeof audio amplification in a radio receiver and other electric translating systems. The arrangement of the five electrodes in the tube reduces the inherent capacity of the tube to a negligible. quantity.

Viewed in another aspect, my invention comprises an electronic tube in which at least one set of operative electrodes is supported by novel means in such a way that the electrodes are braced at the top and bottom against axial and lateral displacement. This permits rough handling of the tube without danger of disturbing the original alignment of the electrodes.

The novel features and practical advantages of my invention will be understood from a description of the accompanying drawing, in

- which- Fig. 1 is an enlarged perspective view of a vacuum tube constructed in accordance with my invention, certain parts of the tube being sectioned for clearness;

Fig. 2 shows a detached view, partly sectioned, of the electrode assembly and mounting;

Fig. 3 represents a, transverse section on line 3-3 of Fig. 2; and

'Figs. 4 and 5 indicate diagrammatically the circuit connections of the tube and the theory of operation.

A vacuum tube l0 has an assembly of elec- 'trodes,comprising a filament l2, two anodes l3 current through the filament.

, at' l9 to hold the plates in fixed relation. 10

The anodes l3 and i3 are shown in the form of metal cylinders inserted at their ends in circular grooves 20 in plates ,l5 and IS. The grids l4 and M are also cylindrical and their ends fit tightly in circular grooves 2l'in plates l5 and I6. As seen in Figs. 2 and 3, the circular grooves and 2| hold each pair of electrodes l3l4 and l3'l4 in permanent concentric relation. In the drawing the electrodes are spaced for clearness more than is necessary, but in actual prac- 20 tice the electrodes are mounted as closely together as mechanical conditions permit. The grids I4 and I4 may consist of wire mesh, slotted or perforated tubes, wire wound spirally over an open cylindrical frame, or of any other practical construction. It is understood that the side rods l1 and I1 are not flattened at l9 until after the cylindrical anodes and grids have been properly positioned between the supporting plates I5 and IS. The concentric grooves 20 and 2| facilitate the proper assembling of the anodes and their associated grids.

The filament I! may consist of a single wire comprising a section |2a passing through the common axis of the concentric electrodes l3l4, a second section l2b passing centrally through the concentric electrodes l3'-i4', and a top section l2c which is pushed upward by an expanding coil spring 22. The filament wire l2 passes through small holes in the insulating plates I5 and i6, and these holes are so arranged that the parallel sections I21; and I 2b of the filament are substantially in the center of the two pairs of cylindrical electrodes I3-l4 and l3'-i4' after the parts have been assembled in the supporting frame. The spring 22 holds the filament sections lZa and l2b constantly taut. In the broader aspect of my invention, it is not necessary that the parts i211, l2b and I20 shall be a single wire, but that is the most convenient way to make the filament. In fact, the electrode l-2 may be any element capable of emitting a fiow of electrons when heated. This heating may be efiected in any practical way, as for example by passing a The lower insulating plate l8 carries a pin 23 which is set firmly into the glass press 24 of the tube, whereby the five electrodes are mounted as a unitary structure. The ends of filament |2 are connected to a pair 01 conducting rods or stifl wires 25 and 26, which are connected by wires 21 and 28 to contact pins 29 and 3|) projecting from the bottom of the tube. The two anodes l3 and I3 are electrically connected to the metal side rods l1 and H, which are connected at their lower ends to wires or rods 3| and 32, and wires 33 and 34 connect the conductors 3| and 32 to contact pins 35 and 38. The two grids l4 and M are connected to conducting rods 31 and 38, which are connected by conductors 39 and 49 to' contact pins 4| and 42. The connections between the electrodes and their respective conducting rods are most conveniently obtained by brazing or soldering, but any other practical method may be employed. The six connecting rods or wires 25, 26, 3|, 32, 31 and 38 are set rigidly into the top of press 24, so that they remain firmly in position.

Referring to the circuit diagrams of Figs. 4 and 5, the grids l4 and I4 are connected to the opposite sides of an input circuit 43 which has a coil 44 adapted to receive electric impulses. This circuit is shown in simplified form and might contain such other electric elements as are necessary for proper operation in any particular system. Since the grids are thus connected to opposite sides of input coil 44, they will always be at opposite potential. That is to say, when grid H has a positive charge, the other grid I41 has a negative charge, and vice versa. The two anodes l3 and I3 are connected by wires 45 and 46 to opposite sides of a transformer coil 41, which may be regarded as consisting of two sections 41a and 4112 connected at their junction to the positive side of battery B by a conductor 48. For convenience I shall refer to the coil sections 41a and 41b as coils, because they can be regarded as separate coils connected at one end. When the system is used for amplifying electric impulses or.

for producing altematlng current from. direct current, the battery B represents any suitable source of substantially contant direct current of the required voltage. In that case, the. anodes 3 and I3 are always at positive potential, and the coil 41 constitutes a primary output coil. A

secondary coil 49 is connected to a suitable transsource of current to provide a fiow of electrons to the associated grids and anodes. It is understood that the filament sections |2a and I2!) are heated alike, so as to emit electron streams of substantially the same strength or density.

In the operation of the foregoing system as an amplifier or producer of alternating from direct current, let us assume that at a given moment the grid I4 is positive and grid i4 negative, as

indicated in Fig. 4. Grid l4 therefore attracts the electrons, while the other grid repels them.

Consequently, an electronic conducting path is established between filament l2 and anodel3, this path being diagrammatically indicatedby the dotted area 5|. The circuit of battery B is now closed through conductor 48, 0011 411), conductor 45, anode I3, electronic path 5|, filament l2 and back to the battery through return wire 52. The current passes through coil 41b in the direction of arrow b. When the grid I4 is positive and the other grid 4 is negative, as indicated in Fig. 5, an electronic conducting path 5| is established between filament l2 and anode l3, so that the plate current now passes through coil 41a in the direction of arrow a. In other words, when grid I4 is positive, the plate current passes through coil 41 in one direction and when grid I4 is positive, the. plate current passes through coil 41 in the reverse direction. Putting this differently, I may say that reversals of potential charges on grids l4 and i4 produce amplified reversals of current fiow (i. e. alternating current) in the primary output coil 41, and these alternations of current induce corresponding current variations in the secondary output coil 49, which may be in step-up relation to coil 41.

The reversals of current in output coil 41 produce greater amplification of induced currents in coil 49 than is possible by mere fluctuations of current without actual reversal of fiow. This is in accordance with well known electromagnetic laws. In electronic vacuum tubes heretofore used, the plate current merely fluctuates in response to variations of grid potentials; that is, the

current varies in intensity but always flows in the same direction. By reversing the flow of current in the primary output coil 41, I obtain induced currents of maximum intensity in the secondary coil 49, so that less tubes are needed to obtain the desired amplification in the final output stage of the system.

It is possible that when the-electron path 5| is established between electrodes l2 and I3, as indicated in Fig. 4, the negative grid l4 does not prevent all electrons from reaching the anode l3, so that a very feeble current might fiow through coil 41a in opposition to the heavy current through coil 41b. However, the opposing electromagnetic effect of any such slight current in coil 41a would be practically negligible. This also applies to the momentary condition of the system in Fig. 5. Since the potential charges on grids l3 and I3 are periodically reversed, it is impossible for electrons to accumulate on either grid, so that no grid leak is necessary.

When my new tube is used for rectifying alternating currents, coil 49 is connected to the alternating source and becomes the primary input coil, while coil 41 becomes the secondary input coil. The two grids l4 and M are connected by wires 53 and 54 to opposite sides of coil 49. The coil 44 is of course not required now, and battery B is replaced by a direct-current consuming device. As the current alternates through coil 49, the potential charges on grids l4 and I4 change accordingly, and the induced alternating currents in coil 41 change in the same way. For instance, when the current in coil 49 fiows in the direction of arrow 0, the potential on grid i4 is positive and that on grid I4 is negative. The induced current in coil 41 flows in a direction opposite to the fiow of primary current, so that anode i3 is positive and anode I3 is negative. An electronic conducting path is therefore established between filament|2 and anode l3, so that current flows through translating device B in the direction of arrow d.

Let us now suppose that the current flows through primary coil 49 in the direction of arrow negative. The induced current in coil 41 flows in the direction of arrow b, so that anode I3 is positive and anode I3 negative. An electronic conducting path is established between filament l2 and anode lit to complete the circuit through translating device 3 in the direction of arrow d, the same as before. The entire coil 41 does not operate at each alternation, for the current flow through translating device B in the same direction is completed alternately through coil sections "a and 41b. It is customary to insert choke coils and condensers for smoothing out current ripples in the rectified circuit, as will be understood without further explanation. Since the grids H and H are in an open shunt across coil 49, they consume no power in the operation of the rectifying system.

Although I have shown and described a specific construction of vacuum tube and circuit connections therefor, my invention is not limited to the details set forth. In the broader aspect of my invention the particular form, mounting and arrangement of the electrodes are immaterial, so long as the desired result is obtained. Changes and modifications may be resorted to without departing from the scope of the invention as defined in the appended claims.

I claim as my invention:

1. An electronic vacuum tube having a cylindrical anode, a cylindrical grid within said anode. a support comprising a pair of spaced insulating plates having circular recesses for receiving the opposite ends of said anode and grid to hold the same in concentric relation, whereby the ends of said anode and grid abut against said plates and hold the latter spaced, so that any tendency of the plates to move toward each other increases the pressure of the engagement between said plates and said electrodes, a filament mounted substantially in the axis of said concentric electrodes, and .a plurality of stiff rods connecting said plates independently of said cylindrical electrodes and rigidly holding said plates against separation.

2. An electronic vacuum tube provided with a pair of insulating supports held in spaced parallel relation, a pair of cylindrical anodes mounted rigidly side by said between said supports, a cylindrical grid mounted in each anode, cooperating means on said supports and said grids for holding the latter in substantially concentric relation to the associated anode, said spaced insulating supports holding the two anodes insulated from each other and also holding the two grids insulated from each other, an electronic filament having portions substantially in the axes of said pairs of cylindrical electrodes,,and a plurality of stiif rods connecting said supports independently of said cylindrical electrodes and rigidly holding said supports against separation.

3. An electronic tube comprising a pair of insulating plates, a plurality of rigid electrodes supported by and between said plates, means independent of all electrodes for rigidly connecting said plates and locking them against separation, other means for rigidly supporting the connected plates and electrodes as a unit, and means for locking the ends of said electrodes to said plates,

and electronic means in operative relation to said electrodes.

4. An electronic tube comprising a. pair of insulating plates supported transversely of the tube.

a pair of cylindrical electrodes supported by and between said plates in concentric relation, means independent of said cylindrical electrodes for rigidly connecting said plates and locking them against separation, other means attached to at against separation, said tie-rod being conductive and in electrical contact with one of said electrodes, and means independent of said tie rod for supporting the connected plates and electrodes as a unit.

6. An electronic tube having a plurality oi sets of electrodes, each set comprising a filament, an

anodeand an interposed grid, said anodes being insulated from each other and each anode at least partially surrounding the associated filament, the anode of each set of electrodes being shielded from the electron stream emitted by the filament of the other set, a pair of transverse plates by and between which said sets of electrodes are supported side by side in spaced relation, said plates and the opposite ends of said anodes and grids being in firm engagement, so that. said anodes and grids constitute spacing means for said plates, and a. plurality of stiff rods connecting said plates independently of all electrodes and locking said plates against separation.

7. An electronic tube comprising a pair of insulating plates supported transversely of the tube and provided with circular grooves, a pair of cylindrical electrodes supported by and between said plates, the ends of said electrodes extending into said grooves, whereby said electrodes are locked against displacement, means independent of said cylindrical electrodes for rigidly connecting said plates and locking them against separation, and other means attached to at least one of said plates for rigidly supporting the connected plates and said electrodes as a unit.

8. An electronic tube having a cylindrical anode, a cylindrical grid within said anode, a support comprising a pair of spaced insulating plates rig dly connected, means on said plates for holding said anode and grid in concentric relation, said plates and the opposite ends of said anode and grid being in firm engagement. so that said electrodes consttute spacing means for sa d plates, a filament engaging said plates and mounted substantially in the axis of said concentric electrodes, means independent of said electrodes for locking said plates against separation, and a separate member connected to at least one of said plates for rigidly supporting said plates and electrodes as a unit.

parallel, a rigid insulating support for holding said sections spaced apart, said parallel sections being joined by a transverse section of filament above said support, means carried by said support for tensioning said transverse section to hold said parallel sections taut, said parallel sections being held in spaced relation bysaid support independently of said tensioning means, and at least one electrode in operative relation to each of said parallel sections, each electrode being shielded from the electronic emission of the filament associated with the other electrode.

10. An electronic tube comprising a pair of transverse insulating plates, 9, tie rod for holding said plates against separation, electrodes operatively mounted between said plates, at least one of said electrodes being rigid and engaging said plates and holding them spaced apart, whereby said rod and rigid electrode cooperate to maintain said plates firmly in predetermined spaced relation, and a rigid post connected to at least one of said plates for supporting the connected plates and said electrodes as a unit.

11. An electronic tube comprising a central rigid post projecting from its base, an insulating plate secured to said post, a pair of rods projecting upwardly from the ends of said plate, a second insulating plate engaging the upper ends of said rods and held substantially parallel with the lower plate, means whereby said rods lock said plates against separation and a plurality of electrodes engaging said plates and rigidly held thereby in spaced relation, said electrodes being stiff and holding said plates against movementtoward each other. H

12. An electronic vacuum tube provided with a pair of insulating plates held in spaced parallel relation, a pair of cylindrical anodes mounted' rigidly side by side between said plates, a cylin-: drical grid mounted in each anode and held by ration thereof, said rods being in contact withsaid anodes'and constituting conductors therefor. 13. An electronic vacuum tube comprising a substantially rectangular frame rigidly supported axially of the tube, said frame having upper and lower cross members provided with a plurality of recesses, a pair of electrodes of cylindrical shape supported by and between said cross members in substantially concentric relation, said electrodes having portions extending into said recesses, whereby the electrodes are locked against relative displacement, and a plurality of stiff rods' for connecting said members independently 01- said electrodes and rigidly holding said members against separation. v

14. An electronic vacuum tube containing a one-piece filament which'has two taut sections substantially parallel and held spaced apart, said parallel sections being joined by an integral transverse section, spring-means acting upori the central portion of said transverse section in a direction substantially parallel with said two parallel sections, whereby said'transverse section is held constantly under tension to maintain said two parallel sections taut, and a pair of spaced anodes in operative relation to said filament sections, each anode at least partially surrounding one of said sections and beingshielded from the electronic emission of the other section.

15. An electronic vacuum tube comprising a set of electrodes operatively positioned in the direction of the axis of said tube, said electrodes including an electron-emitting element, a rigid support for said electrodes, said support including a pair of spaced insulating plates for the top and bottom of said electrodes to hold the latter securely against axial and lateral displacement,

'said element engaging said support at the top and bottom only, so that the electron-emitting portion of said element is wholly out of contact with said support, said element passing through the upper plate oi. said support, and means on .said upper plate for engaging said element.

16. An electronic vacuum tube having two cylindrical anodes mounted in spaced relation and insulated from each other, a cylindrical grid mountedcentrally within each anode, said grids being insulated from each other and from said anodes, an electronic filament comprising two parallel sections each of which is located substantially in the axis of one pair of said nested cylindrical electrodes, an insulating cross-plate rigidly supported and engaging the upper ends of said cylindrical anodes and grids to. hold them firmly in position as a unit, and six contact members projecting from said tube and electrically connected to said five electrodes as follows: two

of said. contact members being connected to said here being connected to said pair of insulated grids, and the remaining contact members being connected to the ends of said filament.

--1*7. An electronic vacuum tube having the usual press at the bottom, a rigid post carried bysaid "press, an insulated plate mounted on saidv post, a second insulated plate vertically spaced from b said first plate, an electrode assembly mounted on and between said spaced plates, said assembly comprising at least one cylindrical anode and one cylindrical grid within said anode,

said nested cylindrical electrodes engaging saidplates at bothends and holding them spaced .apart, a plurality of stifi rods connecting said opiates independently of said electrodes and preventing separation of said electrodes, and leadingin wires embedded in said press and connected to said electrodes, said post forming a rigid support for the connected plates and electrode assembly independently of said wires.

18. An electron discharge device having in combination with a cathode and grid, a pair of supporting rods on opposite sidesof said cathode and grid, an anode carried by one of said rods, an insulating plate .at one, end of the anode sea cured thereto, and means for securing said plate with respect to the other support rod.

19. An electron discharge device having in combination with a cathode and grid, a pair of supporting rods on opposite sides of said cathode and grid, an anode carried by one of said rods, an insulating plate at one end of the anode secured thereto, a grid connection engaging said plate for holding it against movement in one direction, and means on the opposite side of said plate for il iolding it against movement in another direcon.

20. In an electron discharge tube, a unitary structure supported therein comprising a hollow plate electrode, insulating caps at the ends of the hollow plate, said caps having annular grooves, a heater-cathode element supported by said caps in axial position within the hollow plate, and a hollow grid supported by the grooves in said caps in surrounding position ,relatively to the heater-cathode, the caps having orifices for the passage of the terminals of the heater-cathode and grid.

21. In an electron discharge tube, a unitary structure supported therein comprising a hollow plate electrode, insulating caps at the ends of the hollow plate, said caps having annular grooves. a heater-cathode element supported by said caps in axial position within the hollow plate, and a hollow grid supported by the grooves in said caps in surrounding position relatively to the heater-cathode, said grid comprising a wire coil to one side of which is welded a terminal wire parallel with the axis of the coil, the caps having holes receiving through them the ends of said grid terminal wire.

22. In an electron discharge tube, a unitary structure supported therein comprising a cylindrical plate electrode, insulating caps at the ends of said cylindrical plate, said caps having annular grooves, a heater-cathode element supported.

by said caps in axial position within the cylindrical plate, a hollow grid supported by the grooves in said caps in surrounding position relatively to the heater-cathode, and means for supporting said unitary structure comprising a sumciently heavy wire projecting from the press of the tube and welded to the side 01' the cylindrical plate.

23. In an electron discharge device, a cathode, a tubular grid, a tubular anode, and insulator caps on both ends of said anode, said caps having concentric grooves for spacing the cathode, grid and anode.

24. An electrode assembly comprising a pair of insulating members and a plurality of electrodes, including cathode, anode and control grid, said insulating members having a number of parallel projections thereon to separate the ends of said electrodes, and means including said projections for maintaining all of said electrodes in concentric spaced relation.

25. An electric discharge device comprising an enclosing receptacle, insulating blocks within said receptacle, said blocks having a plurality of similar projections, and cathode, grid and anode electrodes seated in said blocks and maintained in spaced relation by said projections.

26. A tube comprising an enclosing envelope, a plurality of filaments, a plate adjacent each filament separately surrounding the same, upright supports for the plates, a member fastened tosaid supports and fitting snugly between and against the opposed outer surfaces or the plates and holding the latter from movement relative to each other, said member being in the form of a sheet of insulation mounted in a plane extending substantially atv right angles to the axes of said plates.

27. A tube comprising an enclosing envelope, a pair of spaced cathodes, a pair of anodes each separately surrounding a corresponding one of said cathodes, and a sheet of insulating material extending between the anodes and at right angles to the axes thereof, said sheet having opposed edges abutting against the opposed outer surfaces of said anodes to prevent relative rotation between said anodes and cathodes.

28. A tube comprising an enclosing envelope, a plurality of electron-emitting cathodes, a pair or anodes each separately surrounding 'a corresponding one of said cathodes, a sheet 01' insulating material extending between the anodes at right angles to the axes thereof, said sheet abutting against the opposed outer surfaces of said anodes, and means connecting said cathodes and said anodes to said insulating member in interlocking relation.

29. A tube comprising an enclosing envelope having. a press, a support wire sealed substantially centrally in said press, a pair 01 lateral support wires sealed into said press, a tubular anode fastened to one of said lateral supports, another tubular anode fastened to the other of said lateral supports, an insulator member through which said central support passes and positioned between said anodes in abutting relation with the opposed exterior faces of said anodes to prevent relative rotation therebetween.

30. An electron discharge device comprising an envelope enclosing two spaced substantially parallel rods, two spaced insulating members extending transversely of said rods and attached thereto, tubular electrodes between said insulating members parallel to and individually attached to said rods, the attachment between the tubular electrodes and the rods being eccentric oi the center of said tubular electrodes, means for securing the ends of said tubular electrodes to said insulating spacer members to prevent rotation of said electrodes about said rods as a center, and cooperating cathodes disposed centrally oi the tubular electrodes and held spaced from said tubular electrodes by said insulating members.

31. In an electron discharge device an electrode assembly of the unitmount construction comprising two parallel rods, tubular electrodes parallel to said rods each attached along one side to one rod, spaced insulating members to hold said rods in parallel spaced relation extending transversely between said rods beyond the, ends 01' said electrodes and joined to said tubular elec-- trodes to prevent rotation of said tubular electrodes about said side rods, and cooperating cathodes held inside and in spaced relation to said tubular electrodes.

ADOLPH A. THOMAS. 

